Demand indicator and controller



W. T. CHAPMAN DEMAND INDICATOR AND CONTRLLER Dec. 7 1926.

'Filed Dec. l. 1924 Fig Inventor'. i Wliam Chapman,

His Attorneg.

Fatented Dec. 7, 1926.

urrsn STATES` PATENT OFFICE.

WILLIAM T. CHAPMAN, OF N ISKAYUNA, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

DEMAND INDICATOR AND CONTROLLER.

Applicationled December 1.8, 1924.' Serial 110.756,811.

My invention relates to a demand indicator, particularly adapted for usein connection with electric power installations where an extra charge ismade it the energy is taken at an average rate in excess of an agreedmaximum demand over a predetermined interval.

In such installations it is desirable that the consumer shall not exceedsome previously established maximum demand. On the other hand, it isusually more economical for the consumer when he uses power up to themaximum demand limit. It is therefore desirable that a device beprovided which will indicate at all times during any demand interval,the maximum load which may be carried during the remainder of the demandinterval to reach but not exceed the established maximum demand.

My invention relates to such a device. The device is also preferablyarranged to indicate the maximum demand reached during a month or otherdesirable period, the integrated consumption during any part of a demandinterval, and the time over which suc-h consumption is integrated.

The features of my invention which are believed to be novel andpatentable will be pointed out in the claims appended hereto. For abetter understanding of my invention, reference is made in the followingdescription to the accompanying drawing in which Fig. 1 represents achart to be referred to in explaining the principle of my invention;Fig. 2 represents a perspective view of apparatus for carrying out myinvention; Vand Fig. 3 is a detail of construction of the apparatusrepresented in Fig. 2.

e Referring now to Fig. 1, 10 represents a chart graduated inrectangular coordinates. The chart is provided with vertical linesrepresenting time graduations. In the present case these graduations aremarked per cent of interval remaining. Thus, if an indicator 11 be movedfrom the left side of the chart toward the right at a uniform rate suchthat it would travel over the chart in a demand interval, theindications along the top of the chart will show at any instant the percent of the time interval remaining.

The horizontal lines of the chart are representative of the per cent ofallowable maximum demand remaining and are so graduated. For example, ifthe maximum de- `mand allowable during a particular time interval is1000 kilowatt hours and 800 kilowatt hours are consumed in the firsthalf of the demand interval, only 200 kilowatt hours, or 20% of theallowable demand, remains. It an indicator 12 is moved relative to thechart, starting at the upper side at the beginning of a demand intervaland moved downward at a rate proportional to the consumption of electricenergy, such that when the consumption over the demand interval is equaltothe allowable demand, the indicator reaches the bottom of the chart atexactly the end of the time interval, the indicator will correctlyindicate the per cent of allowable demand remaining at any instantduring the demand interval. The chart is also provided with a series oflines `radiating from the lower right hand corner which arerepresentative of the per cent of rated load which may be carried duringthe remainder of a time interval, which value is indicated by thecrossing point 13 of the two indicator arms 11 andk 12. By rated load Imean the average load which may be carried to reach, but not exceed, themaximum allowable demand. Thus, if the indicators 11 and 12 starttogether at the beginning of a demand interval at the upper left handcorner and the load is just equal to the rated load, the intersection ofthe two indieating rods will follow the true diagonal line of the chartrepresentative oi 100% rated load to the lower right hand corner. If theload is' less than rated load, indicator 12 will not move so fast andthe intersection will fall above the 100% rated load line for example,as illustrated in Fig. 1, where the intersection lies between the 150%and 200% rated loadV lines indicating that for the remainder oli' theinterval approximately 17 0% rated load should be held to bring thedemand over the interval up to the maximum allowable demand. If the loadduring the early part of the demand interval had exceeded the ratedload, indicator 12 would tit] have moved faster so as to bring the intersection ofthe two indicating` rods below the 100% line, for example atpoint .13', indicating that tor the remainder ot the interval only 10%ot the rated load should be carried it the allowable maximum demand torthe interval is not to be exceeded. Tfilhile the various graduations arerepresented in per cent, they may be given in the units actually used,tor example, minutes, kilowatt hours and lilowatts.

ln Fig. 2, l have represented apparatus tor carrying out the indicatingprinciple just explained. ated similar to that represented in Fig. 1, isplaced upon the suriace oi a drum 15 Vin the form ot a cylinder with thetop and bottom ot the chart coming together on a horizontal line of thecylinder represented at 16. rl`he cylinder, and with it the chart,

i., rotatable with a shaft 17- at a rate proportional to the consumptionot electric energy in the direction or" the arrow 18. rlhe means otmovingthe chart consists in this instanc 19 and 20, ratchet wheel 21,ratchet pawl 2.2, armature lever 23 and relay 24. Relay 211 is in thecircuit ot' contacts 25 and a source of supply 26 and the contacts areclosed by the watthour meter 26 at a rate proportional to theconsumption ot energy measured by the meter. A timing device 27 operatesa cam wheel 28 which cooperates with a lever 29 having a torlred end 30engaging the slidable pinion gear 20. fit the end oi" demand interval asdetermined by the timing device, pinion 2O is thus disengaged Ifrom gear19 and a spring 31, which is wound up when the chart is advanced,returns the chart and drum to a lzerl posik tion such as is indicated inthe drawing, with a projection 32 on the drum against a stationary stopExtending from the right of stop 33 is an indicator which cooperateswith a scale 34e on the `end ot drum 15, whereby the demand over anypart ot an interval is indicated. Extending from the lett ot stop 33 isan indicator which cooperates with a scale on the surface ot a separatedrum 36. rlhe drum 36 is inde pendently pivoted on the support 37 Vandis rotated by means ot the projection 32 on drum and a linger 38 on drum36 when the drum 15 isrotateo in the direction ot the arrow 18. lWhendrum 15 is reset to a zero position, drum 36 remains in the posi tion otmaximum rotation and thus indicates the maximum demand over a number offsuc cessive intervals, for example over a period of a month, or oversuc-h other time as is desired after which the drum 36 is reset againstprojection 32 by hand.

Adjacent the chart 10 is a stationary time scale 39 and cooperating withthis scale and with chart 10 is a time controlled indicator 10. Thisindicator 40 is secured to a flexln this ligure a chart 10, gradureichenible cord el which passes over pulleys l2 and 43 ends ot the cord areprovided with weights la and weight a being somewhat heavier than weight45. Pulley 13 is normally driven in a direction to move cord fil, andwith it indicator 110, to the right, by the timing device 2T to whichpulley i3 is mechanically connected through shat-t 46 and gears iT-i8.

rit the end ot a demand interval as determined by the cam wheel 28, gear4i' is moved away from gear i8 by reason ot the connection 49 betweenshaft and cam lever 29, so that when `thus disengaged, weight lfl tailsand moves the indicator 41.0 .against a stop 50 and positionsr indicatorel() at :the lett hand end ot the time scaleV 39 and .the chart 1(7).

rlhe `position ot JThe parts represented in 2 indicates the beginningot' va time interval. The rotation ot the meter QGlcauses the actuationof relay 2a and the rotation of drum 15. The driving connection betweenthe meter and drum 15 will he such that for rated load, the drum willmalte one revolution per demand interval. It isnot essential howeverthat the chart occupy the complete circumterence ot the drum and in casethe chart occupies for example threequarters ot the circumference ot thedrum, the gear ratio should .be such as to cause the drum to maltethree-quarters ot a revolution per demand interval with rated load;rl`he clock causes the irflicator to be moved to the right at a ratesach .that it will reach the right hand end ot the chart at the end ot ademand interval. rlhe v indicator is thus caused to cooperate with thechart and indicate thereon the load which should be vheld during theremainder ot any portion ot ademand interval in order to .reach .but notexceed the maximum allowable demand during that interval Yand ythe scale39 to the right .of the indicator l-.O indicates the length 4ot timeremaining in the interi-.tal so that .any time during a demand intervalthe operator can tell just how long he is to hold a given load in orderto obtain lthe maximum operating economy. Tfor example, let vus supposethat during the first hall oit a demand interval, no consumption otelectric Aenergy and no rotation o' the drum takes place. rlhis willbring indicator 110 opposite `the line marlred 200 on the chartindicating that 200% rated load, or 20G lrilowatts Vas the case may be,should be carried over the last hait ot the time interval in order toutilize the maximum amount of power without exceeding the maximum demandrate.

Fig. 3 represents a cross-section through the lett hand end ci the drumyto show one manner ot rotatably apport-ing the parts.

ln accordance with the provisions ot' the patent statutes, l havedescribed the prinat opposite ends ot the drum= rlheV lof? ciple otoperation of my invention, together Awith the apparatus which I nowconsider `to represent the best embodiment thereof;

but I desire to have it understood that the apparatus shown anddescribed is only illustrative and thatthe invention can be carried outby other means.

l/Vhat I claim as new and desire to secure by Letters Patent of theUnited States, is-

l. A rate indicator comprising in combination a device operating at aconstant rate, a device operable at a variable rate, and time controlledmeans for establishing predetermined time periods and for establishinginitial indicating positions of said two devices at the beginning ofeach such period, said two devices cooperating together over a givenperiod of time to indicate the rate'at which the variable rate devicemust be operated during a remaining portion of such period ot time tomaintain a predetermined average rate over said given period of time.

2. A rate indicator for power installations comprising in combination atiming device, a meter, and two indicating` devices, one operated at arate proportional to the timing device and the other operated at a rateproportional to that oi' the meter, and means for establishing initialindicating positions of' said two indicating devices at predeterminedtime intervals whereby the rates oi said two indicating devices may becompared .over a given interval of time to obtain an indication ot' therate at which the meter should be operated during any remaining portionof said given interval of time to maintain a predetermined average rateover the whole interval.

3. A demand meter for power installations comprising an energy meter, agraduated member' operated at a rate proportional to the rate oi' themeter, a timing device, means operated by said timing device forperiodically resetting said member to an initial position, an indicatoroperated by said timing device, said indicator cooperating with saidgraduated member to indicate at all times during a demand interval therate at which the energy meter' should be operated during the thenremaining portion of the demand interval to maintain a prel` determinedaverage rate over the whole interval. i

4L. A rate indicator comprising in combination a time controlledindicator and an indicator operable at a variable rate, said twoindicators cooperating together to in dicate the rate at which the lastmentioned indicator should be voperated during any remaining part of agiven period of time to maintain a predetermined average rate over saidgiven period of time, and means for indicating such remaining portion otthe given period of time.

5. A demand indicator comprising a meter, a. graduated member operatedat a rate proportional to said meter, a timing device, an indicatoroperated thereby, means controlled by said timing device for resetting'said graduated member and indicator tozero positions at the end of eachdemand interval, said member and indicator cooperating together toindicate the rate at which the meter should be operated during anyremaining portion of a demand interval to maintain a predeterminedaverage rate over the whole interval, and means operated by said timingdevice for indicating such remaining time.

6. In combination, an integrating type meter, a timing device, a timeindicator, a rate chart having rectangular dimensions respectivelyrepresentative ot time and rate units, means for moving said chartrelative to a zero reference line in the direction ot the rate unitdimension at a rate propor tional to that of the integrating meter,means for moving the time indicator along said reference line in adirection of the time unit dimension at the rate of the timing device,and means for resetting said movable devices to a zero position withsaid time indicator on said reference line at one corner of the chartwhen said time indicator has traversed the chart.

7. In combination, an integrating meter, a timing device, a rate chart,an indicator cooperating with said chart, means responsive to theintegrating meter for producing relative movement of said chart andindicator in one direction during a demand interval, and meansresponsive to the timing device for producing relative movement ot saidchart and indicator in another direction during the same demand intervaland producing by their combined movements an indication at all timesrepresentative oi the rate at which lthe meter should operate during theremainder of the demand interval to maintain a predetermined rate overthe total demand interval.

8. In combination, a cylindrical rate chart, an integrating meter, meansfor rotating said chart on its axis at a rate proportional to that ofthe meter, a timing device, an indicator cooperating with said chart,means responsive to said timing device for moving said indicator axiallywith respect to the chart, means for setting said chart and indicator tozero positions at predetermined intervals of time, and graduations onsaid chart with which said indicator cooperates to indicate at all timesbetween the reset periods the rate at which the meter should be operatedduring the then remaining part ofsuch interval to maintain apredetermined average rate over such predetermined interval.

9. In combination, an electric power circuit sub'jeet'to t Variablerateoffenergy flow, an electric meter for measuring-'the energ57 ofSaidk circuit, a maximum demand meter associated with said'energy meterfor metre'- uring the maximum demand oi said circuit over predetermineddemand intervals, and means associated with said demendineter for mendVintervals to reaelr buty not exceedv a.'

predetermined dem-fund.

in Witness whereof, Iliave hereuntosetmy hand this 17thy dayv ofDecember, 19242 VILLIAM T, CHAPMAN.

